- Tests can be used to identify anions in solutions of unknown compounds.
- If multiple tests are being carried out on the same solution it is important to carry them out in the same order as in the table below
Tests for solutions containing one or more unknown anions
- Ammonia can help distinguish between the silver halide precipitates
- Silver chloride dissolves in dilute ammonia
- Silver bromide dissolves in concentrated ammonia
- Silver iodide is insoluble in concentrated ammonia
Testing for transition metal ions
- Adding aqueous sodium hydroxide to various transition metal ions produces precipitates.
- These reactions can be used for identifying transition metal ions in an unknown solution
The reactions of aqueous transition metal ions with aqueous sodium hydroxide
Testing for ammonium ions
- When heated with hydroxide ions ammonium ions react to produce ammonia gas
NH4+ (aq) + OH- (aq) → NH3 (g) + H2O (l)
- Any ammonia produced will turn damp red litmus paper blue confirming the presence of ammonium ions in the original solution